question.md

Vending machine (beverage)

1. There are items in the vending machine like coke, soda, pepsi each with a particular price.
2. A user should be able to get prices of all the items in the machine.
3. A user should be able to select any item and insert cash to buy it.
4. The machine only performs one activity at a time. For eg If the machine is in process of dispensing an item, the user can't try to buy a new item or insert cash.
5. The machine should display appropriate error messages in every situation. For eg in above condition it can throw "already dispensing item can't select a new item".
6. The vending machine should also return the remaining change after dispensing the item if any.

Assumptions A single slot in the vending machine User can only buy one item of any type.

Schema:

1. Items

   1. id
   2. name
   3. vending_machine_id
   4. price
   5. quantity
   6. meta-data

2. Transaction

   1. id
   2. item_id
   3. price - 30
   4. payment_method - ENUM -> CASH, CREDIT
   5. credit_amount - 50
   6. debit_amount - 20
   7. status - CAPTURED, CREATED, FAILED
   8. reason

3. VendingMachine

   1. id
   2. name
   3. meta-data

4. Denominations

   1. id
   2. vending_machine_id
   3. denomination
   4. quantity

-> APIs POST -> /item/add/{vending_machine_id} { 'name', price }

GET /item/all/{vending_machine_id} -> Table: Items { id items: [{}, {},....] } GET /item/{item_id} -> Table: Items { id: . . }

POST /buy/ { item_id cash } Status code: 200 OK status code: 403 Forbidden request